Blow-molded container having reinforcement ribs and method and apparatus for making same

ABSTRACT

A blow-molded plastic container ( 10 ) providing enhanced top loading capability. The container ( 10 ) has an inner peripheral surface ( 24 ) on which a plurality of integral, solid, inwardly and longitudinally extending ribs ( 26 ) are formed. Preferably, the ribs ( 26 ) extend throughout the entire container inner surface ( 24 ) from the top edge of the finish ( 20 ) to a mold parting line ( 28 ) on the base ( 14 ). A method and apparatus for making the container ( 10 ) is also disclosed.

This application claims priority from provisional application Ser. No.60/112,462, filed Dec. 16, 1998.

FIELD OF THE INVENTION

The present invention relates to a sturdy blow-molded container madefrom a minimum of plastic, and more particularly, the present inventionrelates to a container having integrally formed inwardly extending ribswhich enhance container stability and improve container top loadingcapabilities. The present invention also relates to a method and anapparatus for making a reinforced blow-molded container.

BACKGROUND OF THE INVENTION

Various household, automotive and other products, such as liquid,granular or gel products, including shampoo, detergents, motor oil,etc., are commonly packaged and sold to consumers in relativelysmall-sized, plastic, blow-molded containers, or bottles. For example,in excess of two billion one quart/one liter sized blow moldedcontainers for packaging motor oil are sold annually in the UnitedStates alone. Because of the volume of the sales, improvements to thepackaging of such products is of significant concern to the packagingindustry and to consumers, especially those improvements which relate tothe cost of the packaging and its structural capabilities relative toexisting packaging.

Plastic blow-molded containers can be manufactured in a variety ofshapes and sizes from a variety of plastic materials in any number ofknown blow molding processes. For instance, many containers are madefrom high density polyethylene (HDPE) in an extrusion blow-moldingprocess. The containers are required to have sufficient rigidity so thatthey are able to withstand the rigors of filling, stacking, shipping,handling and eventual use by the consumer.

A significant expense incurred in the manufacture of blow moldedcontainers is the plastic required to make the containers. For instance,a typical one quart blow-molded oil container which meets stabilityrequirements may be manufactured from about 51 grams of HDPE.Significant savings can be achieved by reducing the amount of plasticrequired to make each container. As an example, assume that HDPE is soldat 40 cents/pound (0.09 cents/gram), that a reduction of three grams ofplastic per container can be achieved, and that 100 million containersare to be produced for a given year. The reduction of three grams ofHDPE per container results in a savings of $27 million for the year.

The degree of container rigidity required for packing and shippingpurposes limits the ability of manufacturers to reduce the amount ofplastic consumed in the manufacture of containers. This is becausefilled containers are packed in bulk in cardboard boxes, or plasticwrap, or both and placed on shipping pallets. A bottom row of packed,filled containers may support several upper tiers of filled containers,and potentially, several upper boxes of filled containers. Acommercially-satisfactory container must be sufficiently rigid to resistdistortion under these top loading conditions.

The rigidity of containers is measured by vertical compression tests andis referred to as top loading capability. For instance, a one quart oilcontainer may require a top loading capability of about 45 to 50 pounds.A reduction in the amount of grams of plastic in the container canresult in a decrease in top loading capability, unless design changesare made to offset the inherent loss of strength due to a reduction inthe amount of plastic. Thus, for every container configuration, abalance must be achieved between minimizing the amount of plastic forcost saving purposes and providing a sufficient amount of plastic toprovide container rigidity.

Ribs have been utilized in containers for reinforcement purposes. Forinstance, U.S. Pat. Nos. 5,048,977; 4,781,880; and 4,890,757 which allissued to Robbins III, disclose extrusion blow molding containers withalternating ribs and non-self-supporting webs so that the containers arecollapsible in a storage condition and self-supporting in an openposition. Also, U.S. Pat. Nos. 3,956,441 and 4,170,622 which issued toUhlig disclose blow-molded containers having interior ribbed surfaces.U.S. Pat. No. 3,114,932 issued to Donnelly; U.S. Pat. No. 4,496,301issued to Mozer et al.; U.S. Pat. No. 4,869,862 issued to Bryan; U.S.Pat. No. 5,057,267 issued to Seizert et al.; U.S. Pat. No. 5,198,161issued to Ogura et al.; U.S. Pat. No. 5,330,342 issued to Linss et al.;U.S. Pat. No. 5,486,333 issued to Mavridis et al.; and U.S. Pat. No.5,620,722 issued to Spina disclose various methods and apparatus forextruding substantially tubular parisons which have walls withnon-uniform thicknesses and which are intended for blow molding.

Although the above referenced ribbed containers may functionsatisfactorily for their intended purposes, there is a need for a novelblow-molded plastic container which has an exterior configurationsimilar, or identical, to that which consumers have favored, but whichis capable of being manufactured from a reduced amount of plastic whilehaving the same or increased top loading capability. Preferably, thecontainer should be produced according to a novel extrusion blow moldingprocess by apparatus having an extrusion head with a uniqueconfiguration that forms longitudinal integral reinforcing ribs on theinterior of the container.

OBJECTS OF THE INVENTION

With the foregoing in mind, a primary object of the present invention isto provide a blow-molded plastic container which has an exterior surfaceconfiguration substantially identical to currently favored containersbut which has a reinforced inner surface providing a desirable toploading capability.

Another object of the present invention is to provide a container whichprovides a sufficient amount of top loading capability while affording areduction in the amount of plastic used to manufacture the container ascompared with known like-sized plastic containers.

A further object of the present invention is to provide a novel methodof manufacturing a container having an inner surface with integrallongitudinal reinforcement ribs.

A still further object of the present invention is to provide apparatuswhich is capable of extruding a longitudinally, internally, ribbedparison and which has a uniquely configured extrusion head.

SUMMARY OF THE INVENTION

More specifically, the present invention provides a plastic blow moldedcontainer having an inner surface with integrally-formed,longitudinally-extending, inwardly-projecting ribs. At least some of theribs extend continuously from the container finish, vertically along thecontainer sidewall, and into the container base. Preferably, at leastsome of the ribs extend continuously throughout the entire distance ofthe container from the top edge of the finish to a central mold partinglocation on the base. The ribs, which are not visually perceptible whenviewing the exterior surface of the filled container, permit thecontainer to be made from a reduced amount of plastic while providingthe required amount, or better, of top loading capability.

According to another aspect of the present invention, a novel method ofmanufacturing a container is disclosed. In it, a substantially tubularparison having an inner peripheral wall with a plurality ofspaced-apart, inwardly-projecting, solid ribs is extruded and thenpositioned within a blow mold. The parison is expanded under pressureinto the walls of the blow mold thereby forming a container. The ribs ofthe parison become ribs on the inner surface of the container andprovide a longitudinal reinforcement function, primarily in thesidewalls of the container.

According to yet another aspect of the present invention, apparatus formaking the reinforced containers is disclosed. The apparatus utilizes aunique star-shaped mandrel which cooperates with a tubular orifice topermit a substantially tubular parison to be extruded with continuous,longitudinally-extending ribs on an inner peripheral surface of theparison.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the presentinvention should become apparent from the following description whentaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partially cut-away perspective view of a container embodyingthe present invention;

FIG. 2 is a cross sectional view of the container of FIG. 1 taken alongline 2—2 and looking in a direction toward the container finish;

FIG. 3 is a cross-sectional view of the container of FIG. 1 taken alongline 3—3 and looking in a direction toward the container base;

FIG. 4 is a partially cut-away cross-sectional view of a parisonextruded from an extrusion head and located between an open pair ofblow-mold halves;

FIG. 5 is a cross-sectional view of an extrusion head taken along line5—5 of FIG. 4;

FIG. 6 is an elevational view of a mandrel used to extrude a ribbedparison according to the present invention;

FIG. 7 is a cross-sectional view of a peripheral portion of the mandrelof FIG. 6 taken along line 7—7;

FIG. 8 is a partial cross-sectional view of a closed blow-mold having aninner cavity against which a parison has been blown to form a container;and

FIG. 9 is a cross-sectional view of the blow-mold and blown parisontaken along line 9—9 of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a blow-molded plastic container, or bottle, 10 havinga typical configuration for packaging a fluent product, such as in thisinstance, shampoo. Generally, such a container 10 is produced by anextrusion blow molding process in high speed, automated machinery. Sucha bottle 10 is typically made of a sufficient amount of plastic, such ashigh density polyethylene (HDPE), so that the container provides apredetermined minimum level of top load capability.

As illustrated in FIG. 1, the bottle 10 has a cylindrical sidewall 12extending between a base 14 and a shoulder 16. The sidewall 12 has agenerally smooth exterior surface 18 on which labels (not shown) areglued or printed. The shoulder 16 has a finish 20 with threads 22 forcooperatively engaging a threaded cap (not shown). Typically, thesidewalls of such a container have a substantially uniform thickness andan inner surface which is smooth like the exterior surface.

In contrast, the container 10 according to the present invention has aninner surface 24 with a plurality of inwardly and longitudinallyextending, solid ribs 26 which stiffen and reinforce the container 10longitudinally. As illustrated in the cut-away portion of FIG. 1, theribs 26 are spaced-apart and extend continuously in a vertical directionthroughout the sidewall 12. Preferably, as illustrated in FIGS. 2 and 3,the ribs 26 also extend continuously onto the base 14 to a central moldparting line 28, and onto the shoulder 16 through to a top edge 30 ofthe finish 20. Thus, the ribs 26 extend throughout the entire extent ofthe inner surface 24 of the container 10.

Since the ribs are continuous, the ribs extend through the various bendsor corners formed in the blow molded container to reinforce thecontainer at these locations and prevent deformation at such junctures.For example, the container 10 has a corner 58 a at the juncture of thesidewall 12 and shoulder 16; a corner 58 b at the juncture of thesidewall 12 and base 14; and a corner 58 c at the juncture of theshoulder 16 and finish 20. The ribs 26 extend on the inner surface 24across the junctures, or corners, 58 a, 58 b and 58 c to reinforce andstiffen the container 10 at these locations which otherwise would buckleat unacceptable levels of top loading. Other container configurationsmay have several other such junctures, such as, at label bumpers.

The number, size and spacing of the ribs 26 can vary depending on thedesired level of reinforcement desired. By way of example, and not byway of limitation, the sidewall 12 of the container 10 illustrated inFIG. 1 has an outer diameter of about 2{fraction (3/16)} inches and aninner surface with 60, equally spaced and sized,longitudinally-extending ribs 26. Each rib 26 extends inwardlyapproximately 0.002 to 0.015 inches from the inner surface 24 of thesidewall 12 and is about 0.010 to 0.125 inches wide. Each rib 26 has acurved bead-like shape in transverse cross section, but could have othercross-sectional shapes, such as, triangular. The container 10 isdesigned so that it has a capacity of about 2 to 64 ounces, is made fromabout 6 to 100 grams of HDPE, and has an improved top loading capabilityup to 20% relative to a similarly constructed ribless container.

When a container 10 is made from HDPE, or like plastic, the ribs 26 arenot visually perceptible when viewing the exterior surface 18 of thefilled container 10. In addition, most known container configurationswhich are produced by blow molding techniques can be blow molded withthe ribs 26. Thus, container configurations which are already known andfavored by consumers and which provide brand recognition, can be blowmolded in the same molds to produce identical appearing containers whichdiffer only in that ribs are blown integral on the inner walls of thecontainer to structurally reinforce and stiffen the container. If agiven container is made from an equal amount of plastic, the ribbedversion of the container made according to the present invention willprovide enhanced structural performance, such as greater top loadingcapability. Alternatively, if the ribbed version of the container is toprovide similar structural performance as the prior art non-ribbedversion, the ribbed container can be manufactured from a reduced amountof plastic, and thus provide a cost savings. Such savings becomesignificant when large quantities of a specific container design aremanufactured. In addition, such a container provides less plastic whichneeds to be recycled and weighs less thereby reducing shipping costs.

As previously mentioned, one contemplated type of container on which theribs can be utilized to provide significant cost savings is the typicalone quart/one liter motor oil container. Such containers generally havea substantially rectangular configuration and are well known in the art.For comparative test purposes, such a container was manufactured withthe reinforcement ribs according to the present invention. The number,shape, and size of the ribs were similar to that of container 10illustrated in FIG. 1. One of the containers tested was made of 47.8grams of HDPE and provided 89 pounds of top loading capability, andanother tested container was made of 46.6 grams of HDPE and provided 76pounds of top loading capability. Both of the tested containers,provided a greater top loading capability then an identical appearing,prior art, ribless container which was made from more grams of plastic.Therefore, although all three containers visually appeared to beidentical, the containers manufactured according to the presentinvention provided a cost savings and were structurally superior.

While only certain container structures are illustrated or discussedherein, the present invention can be used to produce a wide variety ofblow molded container configurations. Preferably, a container made inaccordance with the present invention will have about 30 to 180 numberof ribs which extend inwardly within a range of about 0.002 to 0.015inches and which have a width of 0.010 to 0.125 inches.

The number and size of the ribs typically depends on the size of thecontainer body; for instance, a bottle having a 100 ml capacity may have39 relatively shallow ribs, whereas a bottle having a 3 liter capacitymay have up to 180 relatively deeply extending ribs. Preferably, theribs are spaced 0.020 to 0.250 inches apart and are continuous from themold parting line on the top of the container to the mold parting lineon the base of the container. In addition, while the ribs are locatedthroughout the entire inner surface of the container including the baseand finish, they need only extend in the sidewall.

DETAILED DESCRIPTION OF THE PREFERRED METHOD

The container 10, discussed above, is produced by a novel method whichis best illustrated in FIGS. 4 and 8. Molten plastic 32 is extrudedthrough an extrusion head 34 to form a downwardly depending tubularparison 36. The extrusion head includes a die 38 and a mandrel 40.

As illustrated in FIG. 4, a pair of mold blocks 42 are positioned in anopen condition adjacent the downwardly extending parison 36. When theparison is extruded a sufficient distance, the mold blocks 42 closearound the parison 36 as illustrated in FIG. 8. A blow pin (not shown)is inserted into the mold 42 and the parison 36 to inflate the parison36 into a container 44. After the container 44 is removed from the mold42, the plastic moil 46 is removed and recycled.

A unique aspect of the method of the present invention is that theparison 36 is extruded with an inner peripherals wall 48 that has anumber of continuous, longitudinally and inwardly extending ribs 50.Thus, the resulting container 44 is formed with ribs extending inwardlyfrom the inner surface 52 of the container 44, preferably, continuouslythroughout the full length of the parison 36 and the container 44. Theribs 50 reinforce and stiffen the container 44 axially to provide itwith enhanced top loading capability. The number, shape, size andspacing of the ribs 50 can vary such as discussed previously.

DETAILED DESCRIPTION OF THE PREFERRED APPARATUS

The extrusion head 34 utilized to extrude a ribbed parison 36 includes amandrel 40 cooperatively positioned a spaced distance from and within adie 38. The mandrel has a frustoconical tip 54 with a plurality oflongitudinally extending grooves 56 as illustrated in FIGS. 5-7. Therelative spacing of the mandrel 40 relative to the die 38 determines thethickness of the extruded parison; while, the number, depth and spacingof the grooves 56 determine the number, size and spacing of the ribsformed on the inner peripheral wall of the parison.

The plurality of grooves 56 provide the tip of the mandrel with a“star-shaped” configuration and provide the tubular parison withcontinuous, inwardly and longitudinally extending ribs throughout thelength of the parison. Preferably, the mandrel has about 30 to 180grooves each having a depth of about 0.015 to 0.030 inches. As bestillustrated in FIG. 7, each groove 56 can be V-shaped in transversecross section with the legs of the V-shape formed at an angle “A” ofabout 45 to 75°. A peripheral arcuate land 60 is formed between eachV-shaped groove 56 and has a width “W” of about 0.002 to 0.010 inches.The mandrels are designed to be readily interchangeable so that theextrusion head can be easily adjusted to extrude any number of ribsdepending on the mandrel installed.

The described container, method of making the container, and apparatusfor making the container provide a sturdy package for fluent products ata reduced cost. The container provides the required amount of toploading capability yet is made from less plastic. The invention can beapplied to existing container designs so that an already favoredcontainer can be improved by making it sturdier or with less plastic.The containers can be efficiently and inexpensively blow-molded, withoutrequiring expensive changes to already existing blow molds, from any ofseveral commercially-available plastics, such as HDPE, and provide anaesthetic appearance despite the rigors of filling, handling and toploading.

While a preferred container, method of making the container, andapparatus for making the container has been described in detail, variousmodifications, alterations, and changes may be made without departingfrom the spirit and scope of the present invention as defined in theappended claims.

What is claimed is:
 1. A container, comprising: a plastic extrusionblow-molded bottle-shaped container body (10) having an inner surface(24), a base (14) having a mold parting line (28), a sidewall (12)extending upwardly from said base (14), a shoulder (16) extendinginwardly and upwardly from said sidewall (12), and a blow moldedupstanding finish (20) extending from said shoulder (16) defining adispensing opening in said container body (10); and a plurality ofinwardly-extending, solid ribs (26) integrally formed on said innersurface (24) of said container body (10), each rib (26) extendingcontinuously from a top edge of said finish (20) to said mold partingline (28) on said base (14) such that each rib (26) extendslongitudinally on said sidewall (12).
 2. The container (10) according toclaim 1, wherein said inner surface (24) has regions withjuncture-forming structures (58 a, 58 b, 58 c) and wherein said ribs(26) extend continuously through said juncture-forming structures (58 a,58 b, 58 c).
 3. A container (10) according to claim 2, wherein acorner-like structure (58 a) provides one of said juncture-formingstructures between the sidewall (12) and the shoulder (16).
 4. Thecontainer (10) according to claim 2, wherein a corner-like structure (58c) provides one of said juncture-forming structures between the finish(20) and the shoulder (16).
 5. The container (10) according to claim 4,wherein a corner-like structure (58 b) provides one of saidjuncture-forming structures between the sidewall (12) and the base (14).6. The container (10) according to claim 2, wherein said ribs (26) areequally spaced apart in at least said sidewall and total at least 30 innumber.
 7. The container (10) according to claim 6, wherein each of saidribs (26) extends inwardly from said inner surface (24) in a range fromabout 0.002 to 0.015 inches.
 8. The container (10) according to claim 7,wherein each of said ribs (26) has a width of about 0.010 to about 0.125inches.
 9. A method of blow molding a plastic container (10), comprisingthe steps of: extruding a parison (36) of molten plastic having an innerperipheral tubular surface with integrally formed, solid, inwardly andlongitudinally-extending, internal ribs (50); disposing said extrudedparison (36) between open mold blocks (42); closing said mold blocks(42) about said internally ribbed parison (36); and blowing said parison(36) in said closed mold blocks (42) to form a container (10) having abase (14) with a mold parting line (28) where the parison is pinchedclosed, a sidewall (12) extending upwardly from said base (14), ashoulder (16) extending inwardly and upwardly from said sidewall (12), ablow molded upstanding finish (20) extending from said shoulder (16)defining a dispensing opening in said container (10), and reinforcementribs (26) located on an inner surface (24) of said container (10) andextending continuously from a top edge of said finish (20) to said moldparting line (28) on said base (14) such that each rib (26) extendslongitudinally on said sidewall (12).
 10. The method according to claim9, wherein said ribs (50) extend continuously throughout the length ofthe parison (36).
 11. The method according to claim 10, wherein saidparison (36) has about 30 to about 180 ribs (50).
 12. A plastic bottleprepared by a process comprising the steps of: extruding a parison ofmolten plastic having an inner peripheral tubular surface withintegrally formed, solid, inwardly and longitudinally extending internalribs; disposing said extruded parison between open mold blocks; closingsaid mold blocks about said parison; and inflating said parison in saidclosed mold blocks to form a container body having an inner surface, abase having a mold parting line where the parison is pinched close, asidewall extending upwardly from said base, a shoulder extendinginwardly and upwardly from said sidewall, a blow molded upstandingfinish extending from said shoulder defining a dispensing opening insaid container body, and a plurality of inwardly-extending, solid ribsintegrally formed on said inner surface of said container body, each ribextending continuously from a top edge of said finish to said moldparting line on said base such that each rib extends longitudinally onsaid sidewall.
 13. A plastic bottle prepared by a process according toclaim 12, wherein said parison is extruded with at least 30 internalribs which are equally and uniformly spaced-apart on said innerperipheral tubular surface of said parison.